The present invention relates to a process for preparing preferably three-dimensionally formable textile sheet structures, such as woven or knitted fabrics.
A preferably three-dimensional forming of a textile sheet structure can be effected for example by deep-drawing, but also by other techniques known per se. Such textile sheet structures are required for example as outer layer or lining for the interior decoration of motor vehicles and, in general, for the lining of plastics moldings. For example, in the case of a metallic inner panel of a door the textile sheet structure can be laid across or be pressed against the surface and be attached with adhesive. Such textile sheet structures can also be used as covering for items of furniture; that is, wherever an uneven, for example relief like surface is to be coated or covered.
The construction of particularly small radii of curvature gives rise to pronounced deformations in the textile sheet material as a function of the thickness of the material of the textile sheet structure used. In the case of knitwear a three-dimensional forming can be effected from the high constructional stretch usually present, but the constructional stretch of a textile sheet structure produces a corresponding reduction in the weight per unit area in the stretched, exposed areas of the shaped article, which can be a visible flaw, in particular in the case of pile material. Unlike knitwear, the constructional stretch of woven fabrics is usually only low and amounts to only a few percent, so that in this case this type of forming is not available.
The formability of sheet structures is distinctly improved by using, for their preparation, elastic yarns, as is described for example in German Offenlegungsschrift 3,405,209. A disadvantage of such stretch fabrics is the low thermal durability of most of the known elastothreads which, under the high processing temperatures of deep-drawing, can even exhibit degradation reactions. A further disadvantage is the residual elasticity of stretch fabrics, which can lead to detachment of the fabric from the base material, in particular in concavely shaped areas with a small radius of curvature.
Nonwoven textiles usually have a high constructional stretch and a high formability which can be improved still further by using undrawn staple fibers or filaments, as is described for example in German Offenlegungsschrift 3,029,752 for the preparation of industrial filters or in German Auslegeschrift 1,560,797 for the preparation of imitation leather. Nonwovens generally have an exterior of uniformly low structuredness. Textile structures can practically only be indicated by appropriate coloring or embossing.
The prior art further discloses preparing woven textiles from undrawn yarns which have been partially oriented by high-speed spinning. For instance, German Offenlegungsschrift 2,623,904 discloses a textile material for clothing purposes which is prepared from high-speed spun, undrawn yarns without further afterdrawing directly by knitting or weaving. German Offenlegungsschrift 1,460,601 and German Offenlegungsschrift 2,220,713 disclose first knitting or weaving partially oriented, undrawn yarns and only then drawing them within the sheet structure. East German Patent 125,918 discloses a process for preparing textile sheet structures in which partially oriented, undrawn yarns are processed by weaving or knitting into a sheet structure and are subsequently subjected to a thermomechanical treatment within the sheet structure.
However, with this previously disclosed process there is a danger that the yarns are drawn nonuniformly in the course of sheet formation (for example during weft insertion on the weaving machine), which results in variable dyeability of the sheet structure.
The prior art also features a description of a particular application where partially oriented, undrawn filaments are heat-set. German Offenlegungsschrift 2,821,243 describes the preparation of weft yarns which are said to protect the belt yarns required in tire manufacture from nonuniform slipping. Particular value is placed in this context on the reduction in free shrinkage at the sort of high temperatures which occur in the vulcanization of tires. This prior art does not say anything about these filaments or yarns being suitable for textile purposes and in particular for preparing irreversibly highly formable textile sheet structures.